Final answer:
Agamemnon's deceptive dream originates from Zeus, leading to a misguided attack by the Achaeans which becomes a major turning point in the Iliad.
Step-by-step explanation:
Agamemnon's deceptive dream emanates from Zeus, who sent it as a means to spur the Achaean army into action.
This dream convinces Agamemnon that victory over Troy was imminent, which leads to a premature and disastrous attack, underscoring themes of fate and divine intervention in the Trojan War narrative.
The dream serves as a pivotal catalyst in the plot of Homer's Iliad, causing a series of events that expose the vulnerabilities and misjudgments of human characters when faced with the whims of the gods.